Answer
22.0 s.
Work Step by Step
The work done on the piano is mgh, assuming y=0 at the start. The work divided by the time interval equals the power.
$$P=\frac{mgh}{t}$$
Solve for the time.
$$t=\frac{mgh}{P}==\frac{(385 kg)(9.80 \frac{m}{s^2})(16.0 m)}{2750 W}=22.0 s$$